Door jamb



June 28, 1938. 4 D, ROBERTS 2,121,826

' Boon JAMB Filed Oct. 2, 1935 INVENTOR.

ATTORNEY,

Patented June 28, 1938 UNITED STATES PATENT OFFICE noon 1m Dudley Roberts, New York, N. Y., assignor to Rubatex Products, Inc., New York, N. Y., a corporation of Delaware Application October 2, 1935, Serial No. 43,133

ZOIaims.

rubber employed, ruggedness against mechanical tear and weather wear are sacrificed with the result that such door jambs have a relatively.

there is described a novel rubber composition (details of which will be given hereinafter) comprising a cellular rubber in which each of the minute cells containing gas at a high pressure are sealed. This sealed cellular rubber is relatively much softer than solid rubber, thus supplying one of the essential properties desired. Inasmuch as each cell is sealed from all other cells, it does not absorb water or moisture from the air and therefore is not so readily attacked by atmospheric conditions. Finally, it may be given considerably greater ruggedness than can be obtained with solid rubber approaching the softness of this rubber.

In employing sealed cellular rubber, however, the method of 'manufacture does not commercially permit the direct molding thereof into the shape of a door jamb.

Accordingly, an object of my invention is to provide a novel rubber door jamb and a novel method of manufacture of the same.

A further object of my invention is to provide a novel sealed cell rubber door Jamb and its method of manufacture.

There are other objects of my invention which together with the foregoing will appear in the detailed description which is to follow in connection with the drawing, in which:

Figure 1 is a perspective view of the side of a 1081" with sliding door, having secured to its edges first necessary to describe the rubber composition which I employ in carrying out my invention.

The ingredients entering into the product are mixed in approximately the following percentages by weight:

- Per cent Washed first grade pale crepe or smoked rubber 40-75 Sulphur- 6-30 Light calcined magnesia 3- 5 Ground gils t 12 Lower melting bituminous substances 12 The base ingredient of the product is the rubber which is preferably of a pale crepe grade #1, obtained in sheets about to x 10" x20".

These sheets of rubber are passed through masticating mills consisting of two rollers rotating in opposite directions as in the case of meshing gears. One roller, however, rotates slightly faster than the other, so that the rubber fed between the rolls tends to rub on the surfaces of the different speed rolls and a nib is formed as shown at H, Figure 2 of the copending application, S. N. 717,550, referred to above. The extent of this nib depends on the relative speeds of the rolls and the nib in turn determines how much of the two surfaces l2 and I3 of the rubber engage and are masticated by the respective rolls M and 15.

The rolls are steam heated to a temperature of approximately 150 F. as the rubber sheets are fed between them. The rubber is masticated or softened in this process, the individual sheets combining into a single mass of soft rubber, the degree of mastication depending on the spacing of the rolls, the temperature and the period of operation. I have found, however, that a mastivided into fine particles and passed through'a' sixteen mesh sieve. While the rubber revolves on the masticating rolls, these particles of bitumin are shovelled on and are uniformly dis,- tributed over the rubber. The heat of the rubber melts the bitumen which penetrates into and is absorbed by the rubber. g

The bitumin acts as a flux at low temperatures in the stage ofpartial vulcanization to be explained hereinafter. Any other low temperature flux may be substituted, 1. e., a low melting hydrocarbon of the asphaltic group of a bituminous or waxy nature, having fluxing properties, such I of the molecular structure apparently occurs: .45

rolling is continued as parafiin wax and steario acid. 'fiurlng stage the rubber has turned'froma light to ajdarkcolor. Ground gilsonite, divided into evenflner par It will accordingly not be'melted by the rubble but will nevertheless penetrate into, impregnate" and be absorbed by'the soft spongy massof --rubber." Gilsonite'functions.asaflux inahigh'tem perature' stage to. be described hereinafter, and r may accordingly be replaced by'any suitablehighf temperature flux such as'a-higlr temperature. asphalt. In using thelexpression -fiux,-- it, will. be understood that I mean asubstance acting to ,amalgamateor assist inthe. vulcaniz1ng. Summarizing the above, three stages have been' described. In the first, the rolls were heated't'o a temperature of 150 F. whilema'sticating or-sofe ordinarily be required for this operation.

In the second stage, a low'temperature flux is applied to the rubber as it continues to pass over the rolls, inthc proportions given above, and this,i by reason of the heat, melts into and is absorbed v g the subsequentfstages to'be described hereinafter.

by the rubber. In the third stage, a high temperature flux is admixed with the rubber while it passes through mastication and result in a rubberimpregnated with ahigh and low temperature hydrocarbon;

The molecular structure of rubber is theoretically described as normally being, in the form-10f a spiral. This may be thought as giving to the rub ber its elasticity and strength. During the working of the rubber described above, a disturbance the rubber tends to lose its natural qualitiesi' tion.

its original condition.

ultimately combine into asoft mass of rubber.

above, are added as thelrollsrcbtat'e. .Sulphur is minutes.

res P rm-11 2' h 'r f b a 'i chine which;

, wings," struts, pontoons'; etc. f forcing operations rubber in the ea c above have .resu

Accordingly, in the next or fourth-"stage, the rubber, now fiat, soft and porous, is permittedtb cool off and is leftto rest for. about i'iwe'lve-hours;- I preferably in a dark; dry room at a temperature of from 80 to 100 F. The; longer [the rest period, the more the rubberregains' its original" condition, but I have found thatitwelve hcurs -f" will ordinarily be suiilcient to'resto'reit to about i The s Of-BJI may resuitin intoxication. ,f r'fthe reasons' When the mass has been formed with adjacent iengaging surfaces adhering, sulphur jand light;

calcined magnesia, in, the proportions given corrected byiPrQVidi-ng a-scond twenty-four hour 'darkirjw r y r q-ata o ature as the previous rest period.

the 's me tem Again'the length ofltlie' rest period inay vary, but .at least twent fou hours is necessary and the of tyvd rOI-leIs rotatiniat' the" same speed. Therubber. is' fed-"betwcen the rolls maintained at a temperaturejo'f -i"rom-1-20P:.to'14 0 F; This is continued-until the rubbe'r.--'again becomes soft and forms lama; uniform, plasticwcomposite mass n during-which the rubber may-be formed into slabs, board v tea-"after which 'a further rest period of'twelve hoursisprovided. 0r, if desired,

passed through 1 a. {forcing ma-' p ferf tduse. for pre-forming the rubberTin any" desired" shape,' such as aeroplane I y-If .preferred, the f ay 'als'ofnbeused to soften the Her, stages described hereinbefore.

The various gesiof gtreatment described in. agitating the rubber to such an extent; ta quantity of air has been absorbed by .th rubber. The presence of-this air may have 'rious i deteriorating effect during This may be described as'followsz- Likeglass, rubberis a plastic or super-cooled viscousliquid. Normally, 'itwould be crystalline,

but ispreVentedfmm becoming so because. of the unstable product. which'tends to stabilize itself.

This is p'articularly' true if the rubber is' warmed tojust below melting point which favors crystaltions is; particularly conducive to crystallization,

; a, simple; oxidation resulting from a; "relatively I s simple'rubbercompound which:crystallizesiout. It is essential to providea rest period for the; rubber at this stage of the operations to permit the rubber to restore itself to itsoriginal condis.

, Moreover,rubber-oxidizeseasily because" it has unsaturationsordoubIe bondsfwhich tend to read- 1 ilycombine' witlr'jthe oxygeirfespecially under the influenced heat and pressure, thus making the ,rubberf .brittle. In 'the presence of air, rubber thereforetendsxtoxoxidize. Attacked or oxidized by 'even. bi'ittle',

g mall amount-O i :a.th rubber becomes siswe l nPwm' T re 'nt this, the;rubher;f-a s- {sci that'it no geniinyth'e air. complex comexpl'alned abova even before vulcanization sets in. rliccording'ly, itgis' ta mororce out all .the air thatrniayfj.have'finiixed with the rubber I H v f beforethestageof partia v the vulcanizer and the light calcined-.magnesia is the rubber toughener." Any equivalentrubber; toughener, such as zinc..oxide; m'ayreplace the 3. calcined magnesia. For thorough absorptiomthe for a period of abouttw'enty- J a Z each-other insuceessivesteps. In the first step, Theproduct is now removed from 'the'rolls in; strips or slabs of about one-half inch in thickness {as shown gin Figure' -l' of the application S. N.

more nearly "the rubber is nd. two i 'lheldistjorting effect of 'passingrthel-rubber.throughgthe rolls is now again 'lization." The presence ofair under these condithe trapped air out and is reduced in size. After the rubber passes the last rolls, a sheet of cloth is applied thereto to close faults appearing in the rubber ,and to prevent the rubber from contracting.- The cloth, having a limited expansion, keeps the stretch in rubber and maintains it a predetermined thickness.

The rubber is now cooled to room temperature and the cloth removed, leaving a sheet ofuntreated rubber. The product is now ready for the two final stages of vulcanization to' be de-' scribed. These vary somewhat for different products. Approximately ten such sheets of rubber may-be placed with metal sheets interposed between each sheet of rubber, and the whole'placed' in a metal container having an internal dimension slightly larger than the combined sheets. A cover is then fastened into place on the container. A number of these containers are then placed into a gassing autoclave which is then closed and fastened down. The autoclave has previously been aired by passing steam through the container and heating it to a temperature of from 180 to 212 F. to remove moisture.

A vacuum pump is then connected to an inlet of the container to extract the air until a vacuum of about five inches is obtained. The evacuation is important for the reasons already pointed out hereinbefore. 'When the container has been evacuated, gas is admitted into the autoclave at a pressure of from 150 to 200 atmospheres. Any inert gas, preferably non-combustible, and having no afiinity for raw rubber, such as nitrogen (N), ammonia (NI-I3) helium (He) may be used for this. Thus air would be disastrous, if used. Forcing air into raw rubber at several hundred atmospheres pressure and at or'near vulcanizing temperatures, would tend to oxidize the rubber very rapidly and before vulcanization set in, resulting in an undesirable product. Moreover, it would be dangerous practice, because a spark would cause a terrific explosion.

While the gas is being forced into the rubber, steam at eight pounds pressure is admitted to the steam chest. About thirty minutes are necessary for the container to reach a stable temperature, and thereafter the container is maintained at the same temperature continuing to supply steam at about eight pounds pressure.

The conditions in this stage are critical and accordingly both the pressure of the gas and the temperature of the container must be correct. The rubber, while exposed to the gas, is in a soft plastic state and therefore readily receives the gas. The eight pounds of steam in the steam jacket produce a temperature at which partial vulcanization proceeds to a substantially uniform degree throughout the body of the rubber. This partial vulcanization functions to harden the rubber sufllciently so that it retains the gas forced into the rubber. At this time substantially little or no expansion of the rubber has taken place due to its confinement within the container.

The autoclave is now permitted to cool ofi under atmospheric conditions and subsequently cold water is forced through the steam jacket until a temperature of 60-70 F. is reached. This permits the rubber now in semi-cured state to set.

Excess gas in the autoclave is now removed. The rubber being partially cured, will hold gas under pressure in its individual cells. The rubber sheets are now removed from the containers with the result that the pressure is removed and the gas in the cells immediately expands .the rubber about four times.

v This partially cured rubber is now placed in a mold suitably constructed to form the shape i shown in Figure 6. 7

As shown in Figure 6, the mold is of a shape to produce rubber symmetrical in shape. comprising two end' portions 2|) and a central ofiset portion ll forming shoulders I and IS with one of the edges of each end portion 20 and shoulders I2 and H with each of the opposite edges of portion 20.

The partially vulcanized rubber placed in the mold for producing this special shape of rubber isnow subjected to the final vulcanization. Each mold is placed in a mold of the desired dimensions. Each mold is placed between platens and saturated steam is applied at ninety-five pounds for about forty to forty-five minutes. This is the final stage of the process of the curing and expansion. The rubber expands to the size of the molds and at the same time complete .curing or vulcanization of the rubber is obtained. The

steam is now turned off and the product permitted to cool. If desired, cooling, may be hastened by applying cold water. The end prod-.

.. completed, must take place within forty-eight hours after the completion of the partial expansion and vulcanization. Otherwise sufllcient gas may escape from the partially vulcanized rubber so that there is a material loss in volume. In the event that more than forty-eight hours elapse before the last stage of the process occurs, it is preferable to regrind the material and add it into the new dough in small percentages.

It is also possible, alternatively, in the event that more than forty-eight hours is to elapse, to take care of this condition by carrying on the first stage to a further degree of vulcanization than originally contemplated by applying the steam for a longer period of time or at a higher temperature than isobtained by eight pounds of steam.

In fact, I have found from experiments that the first stage can be carried on at from eight to sixteen pounds of steam, although better results are. obtained at the lower range. When the greater degree-of vulcanization occurs, the material can be kept for a longer period than fortyeight hours without the gas diffusion.

The final product, depending upon the per centages of the various ingredients used is a soft light rubber of multitudinous minute sealed cells,

each cell apparently containing gas at a high contact with each other. Strips of fabric l8 and l9 (Figure 2) of relatively stiff composition are vulcanized to the rubber along the upper edges of portions 20, fitting against the shoulders I! and I3 and having protruding end portions 3|. These protruding portions may now be secured to the edge of a door 23 (Figure 2) or 24 (Figure 1) by any suitable means as rivets 22. The rubher, when thus secured forms a hollow space H.

The advantages of this construction will now be obvious. Not only does this celltight rubber have a greater resistance to weathering and greater resistance to mechanical inJury, but beordinary rubber.

cause of the minute sealed cells, it provides a greater cushioning effect than is attainable with Moreover, by the special mold, a single inexpensive piece is formed with a hollow space to further increase the cushioning efiect.

In Figures 3 to 5, I have illustrated several of the many modifications my invention may undergo. Thus, I may, if preferred, vuicanize the fabric 26 to the bottom edge of the rubber after the two faces of sections 20 have been brought into opposed relation. Or I may obtain any desired arrangement or shape or number of spaces such as arch 21 and oval 28 in Figure 4 or the two cation of Roberts et al., 21,380, filed May 14, 1935. I do not intend to be limited by the specific formulae, process or mold construction here illustrated, but intend rather to cover door jambs constructed of a sealed cellular rubber in inexpensive single molds. It will be obvious that the usual electrical contactors are placed in the space H and operated when the rubber'is compressed by the closing of the sliding door 24 of car 25.

I claim:

1. A door lamb comprising fabric securing means, soft closed cell gas expanded rubber positioned in adhesive contact with said fabric securing means. the soft closed cell gas expanded rubber constituting the working face ofthe door jamb.

2. A door jamb comprising fabric securing means, soft closed cell gas expanded rubber positioned in adhesive contact with said fabric securing means, the fabric securing means. extending along only a portion of the contacting surface of the closed cell gas expanded rubber.

DUDLEY ROBERTS. 

